Exercise increases creatinine clearance immediately following a workout, assuming one is well hydrated and has good renal function. Dehydration has more serious, longer lasting effect, with the possibility of irrecoverable renal and other damage. Rehydration and supportive therapy are usually effective after acute dehydration, but not always. Medications and foods can affect clearance rates, too. If your test result from a single test is out of expected range, further testing combined with attention to hydration, exercise timing, diet, and medications is indicated. As always, consult your primary care physician! Best wishes.